1. Field of the Invention
The invention relates to an improvement in aluminous refractory compositions containing carbon and silicon, the term carbon including amorphous carbon and graphite.
2. Description of the Prior Art
The excellent ability of aluminous refractories containing carbon to withstand erosion by molten iron and slag is well known and such materials are commonly used to advantage in iron-making foundry and blast furnace facilities, particularly in tap hole and iron and slag spout areas.
The usual carbon refractory materials exhibit the disadvantage of rapid oxidation at temperatures above 900.degree. F. limiting their working life. U.S. Pat. Nos. 3,810,768; 3,846,144; 3,842,760 and 3,923,531, in which applicant is one of the inventors, disclose the combination of powdered silicon metal with carbon along with aluminous refractory material to inhibit oxidation and improve mechanical properties. These carbon refractories also exhibit slag resistance, but their slag resistance is limited by the fact that increasing the carbon content increases oxidation so that there is a practical limit to the amount of carbon that may be used in the composition, generally less than 50% and usually not substantially higher than 35% by weight.
High alumina-chromic oxide compositions are disclosed in Manigault U.S. Pat. Nos. 3,888,687 and 3,948,670. These compositions do not contain carbon in the form of graphite or otherwise. There is no disclosure of the value of chromic oxide in increasing slag resistance and it is believed that such compositions without carbon are relatively ineffective in improving resistance against contact with basic slag compounds.
It is an object of my invention to obtain improved slag resistance without excessive high carbon content in aluminous-carbon refractory compositions.